Hydraulic elevator leveling system



July 12, 1960 w. BECK HYDRAULIC ELEvAToR LEVELING SYSTEM Filed oct. 29,195s ZfzUe/EZW 1M.: .5,4% ai..

Y 2,944,401r I HYDRAULIC ELEVATOR LEVELING SYSTEM v Walter Beck, Moline,Ill., assignor, by mesne assignments, to Montgomery Elevator Company, acorporation of Delaware Filed oa. 29, 1956, ser. No. 618,800

z claims. (creo-52) This invention relates to a hydraulic elevatormechanism, andinparticular it relates to such a mechanism which includesmeans for reducing variations inleveling speed of the elevator in .theup direction due to diierences in elevator loading.

Leveling of hydraulic elevators in the up direction has. alwayspresented a serious problem in the fart. For manyj years the commonestarrangement was to .use asingle speed electric motor drivingA oneliquid.pump, and the' controls were such .that .there was no slowdown or speedreduction as the elevator approached `a.oorr atwhich it'k was to stop inthe other direction. This necessitated. thiat Vthe stopping switches oriloorseleotor contacts `besofset that the elevator-would carry fullloadup .tothe o'o'r, go*V a short distance above the licorv due` toinertiaof.the"`` motor, pump, etc., and then settle'back'lto' iloor levell Ifthe controls are setto carry arull loadto floor level, an empty carnraygo 8 or lOinches past floor level.

An improvement on thisY system consists 4in providingh an up levelingbypass valve Iwhich `opens when the elett/afv Itor'is la 'shortdistancebelow the oorlevel fatwhich a stop is to be made, so that theover-travel ofthe elevator would lbe reduced.

This improvement, however, also has'some disadvan! ftages. When ythebypass valve opens to initiate the vup leveling operation, itinmediately makes the system sensitive to di'erences in .back pressuredue to changesinfthe load 'on the elevator car, because it is obviousthaltthe higher the hack pressure the more rapid will be lthe out-y owthrough the bypass. Typical .pressure variations may range from 100p.s.i. when the elevator car .is emptyj= and 300 psi. when the car isfully loaded. Testreadings ona hydraulic elevator mechanism includinganup level-'1 A ing .bypass valve showed that with full load on ftliecai'the speed during leveling was abo-'ut 5 feet per minute, while'. withthe ycar empty the speed was 30 feet per minute..

1 the llleight'in the elevator car 'and the internal peculiari;

ties of the regulator valve itself. Using a commercially' available flowregulator valve which was not specially designed to compensateiorexternal variations in the system, the variation in up 'leveling speedwas brought .to a

minimumrof'lZ feet per minute and a maximum of 18 feety per minute.vWhenfthe flow regulator valve is specia1ly, tted to the system in whichit is used, this variation may be reduced substantially .to zero.

The invention is illustrated in the preferred embodi` mentfin thevaccompanying drawings in which:

Fig. 1 is Ia schematic piping, valve and control circuit' layout for ahydraulic elevator system embodying the invention; and

Fig. 2 is a central longitudinal sectional view of a flow regulatorvalve which is suitable for inclusion in .the

system of Fig. 1.

.Referring to the drawings in greater detail, the elevatorl systemincludes a liquid reservoir 10, a hydraulic cy1in der 11, an elevatorplunger 12 slda'bily mounted in the 1- cylinder and surmounted by Vanelevator car 13, together with suitable piping, valves and pumpmechanism for moving hydraulic fluid between the reservoir 10 and thekcylinder 11.- Y l A kA main oilsupply Vline 114 connects the reservoir|10 Y if'. with a positivedisplacement pump 15 which pumpshyspeed.

draulic fluid intoia manifold 16, through a shockless check valve 17,Aand Ithrough a second manifold 18 into' the cylinder 11.` The 'pump 15is provided with apulley ISabyfmeans of which the pump may be driven bya belt 15b connect-ed -t-o a suitable electric motor (not shown).fAtypicalfsmall install-ation would have a pump 15 adapted to deliver 50gal-lons per minute when opl era-ted olf ta'n 1800 r.p.m.vmotor at thecorrect operating Control of elevator movement is effected by a pressurecontrolled, normally open starting valve 19, a main down valve 20 and adown leveling valve 21, all of lwhich areA provided 'with suitablecommunications into a ,returnl manifold 22 from which a return line 23car-ries hydraulic A-uid back tothe reservoir |10'. ILeveling of theelevator Obviously, this is a very undesirable situation .in provid'- wing accurate leveling of the car at a floor. Y

In accordance with' the present invention fthe-'bypass line for upleveling is provided with a flow regulator valve of a type in whichpassages 'forl passingiliquid through :the valve havetheir area changedbymovement'l of a valve lpiston so that .the liquid Vwhich-.may passthrough the valve varies inversely :with the hack pressure'i in thesystem which is exerted on the valve piston. With such 'a ilow regulatorvalve inthebypa'ss line, increased load on the elevator car moves thepiston .in a direction to'.

when moving` in the up direction isefrected by means of up levelingbypass means, indicated generally at 24,

which' includes a bypass line 25 which is controlled hy` a solenoid'bypass vala/e126 and, in Ithe illustrated system,

. abattery of three ilow regulator valves 27, 28 |and 29 `whichrarepositioned between an inflow .bypass manifold 370'` and an outflowbypass manifold 31; The bypass valve means '24' perm-its hydraulic uidto be selectively by-lv, passed from the manifold 16 back to the liquidreservoir 10 through the bypass line 25, Ithe manifold 22 and thevreturn line 23. One or more yflow regulator valves may be required,depending on the capacity of the hydraulicf system land of the valves.

The down valves 20 and 21 and the bypass valve 26. A. are :all'providedwith operating solenoids, numbered refv spectively 20a,[21aj'and,26a, vand the solenoids arealli controlled by conventional electriccontrol components.'y

Briefly, the electrical control components may include,

as diagrarnmatically.illustrated in Fig. 1 of the drawing,

l a4 normally open switch 50 whichV is closedv by a suitable reduce theavailable liquid passage area so that the Avol,R

urne of-liquid which mayipass through the ilow regulator valve issmaller when the pressure .due -to elevator car loading is greater.between maximum and minimum speed ofthe car during up leveling. Y t, 1

Proper design of the ilow regulator valve Itoy substantially eliminatevariations in elevator leveling speed due to differences in elevatorload` requires that ,theilow This Itends toreduce the difference;

regulator valve bedesigned to compensatefor flow variaf tions in lthesystem which are due to factors other' than magnetic device'51 (seevBeck Patent 2,843,697) when. elevator car, 13 ascends to yavpredetermined position;- VThe closing of switch -50V connects solenoid26a of the' bypass valve 26 across power` supply leads, 'L1 and L2.,-and, thus, opens valve 26 to permit iluid to flow through" bypassmanifold 30, the ow regulator` valves, and'return line 23.

, The operation of valve solenoids a and 21a to open' valves 20v and 21and e'ect a descent of elevator ear', 13 is controlled by avnorrnallyopen switch 52. .Switch l E52 comprises herein the normally opencontacts of'a con! Patented July 12, 1960I stant pressure push buttonyunit which contacts close when the push .button is Adepressed for Ydownservice and open when the push button vis released. Conventionally, sucha push button unit is 4maintained in the depressed position by.ftheoperator until the elevator reaches :a point slightly iaboye :thepreselected floor level at which it is intended :the elevator :hestopped. The yclosingof switch 52 connects :solenoid 26a .across powersupply leads lLi and l2 :and concurrently energizes a relay coil vv53'Lto close normally y.open :contacts 54 associated .therewith andthereby connect solenoid ,21 also across `power supply leads L1 and L2.Thus, the main descent .operation -of the elevator car is .eifected .byconcurrent opening of valves 20 and ,21.

When the ,elevator car reaches .a point .slightly above the selectedvfloor level .and :the voperator :releases the :push button to.openswitch :52, valve solenoid 20a is ,de-.energized. While coil 53 issimultaneously de-energized ito open contacts 54, an alternative circuittomaintain valve solenoid 21u :energized iis established `to maintainwaive 21 open and thereby lower the car slowly ato rthe :preselectedfloor level. This alternative circuit is established through `a normallyopen switch 56 :closed by a magnetic device 5'5 on the elevator car(-similar to magnetic device 5,-1) and connected in series with ,a relayIcoil 58 controlling normally open relay contacts 59, which :relaycontacts, when closed by Vthe energization of coil `58., bypass contacts54 to energize solenoid 21a. When the elevator car reaches the selectedfloor level, magnet-ic device 55 allows switch :56 to open land therebyde-energize coil 5,8., fwhereupon -contacts 59 open and solenoid 21aopens toclose valve 21.

Similarly, v.operation -of the motor to drive thegpump 15 is leffectedthrough conventional elevator control .com-

ponents.

In operation, assuming Vthe plunger 12 to be .at the bottom of itstravel and rthe elevator car 13 to be positioned .at .the lowest -loorlevel which it serves, operation of the elevator car starting controlstarts up the motor to Aoperate the pump 15 which pumps ,liquid from thereservoir into the manifold )16, and against the check valve 1.7. Thestart-ing valve 19 is normally `opemwhile the down valves 2.0 and 21 andthe bypass valve 26 are normal-ly closed; so that at the .start of.operation liquid from .the pump goes through the starting valve 19 intothe return manifold 22. With ydevelopment of pressure in the system, thestmting valve gradually closes through the operation of pressure valvecontrol head 19a so that liquid passes through the vcheck -valve 17 andinto the cyl-inder 11 to start raising the elevator plunger 12. Whenpressure in the system drops due .to cutting off the pump motor, thecheck valve A17 closes .to ymaintain the plunger in the position whichit ,has reached during pump operation.

When it is desired to move the elevator down, the electric elevatorcontrols open both the down valves 20 and 21 so as to permit rapid llowof .liquid from the cylinder 11 into the manifold 22, and back .to Y.thereservoir 10 through the return line 23. When the elevator car getswithin a short distance of a floor at which it is to stop in the downdirection, the elevator controls close the main down valve 20, but leavethe down leveling valve 21 open. The main down valve closes gradually,and when the elevator reaches floor level the down leveling valve alsobecomes fully closed so that -the elevator may stop .at floor level. Theleveling problem heretofore noted in up operation does not occur whenthe ,elevator is mov-ing down, 'because control of Aelevator travelthrough the two down travel valves ,20 Aand 21 permits accurate levelingof the elevator car at any floor regardless of the load on the car.

The present invention is directed particularly to the up leveling bypassmeans v24J which provides `a relatively uniform up travel leveling speedregardless .of variations in elevator loading.

When .the elevator car approaches a Vdoor at which it is to stop, thecontrol circuit operates as previously described *toppen 'the ynormallyclosed solenoid lbypass valve 26, so the liquid may pass through themanifold 30, the flow regulator valves 27, 2S and 29, the manifold 31and the bypass line 25. It is obvious that the rate of flow of liquidthrough the bypass means 24 will vary with the load in the elevator car13, which will necessarily produce a variation in back pressure .in .the

'- system. Thus, 'with a '-heavy load -on Vthe car, the develing .speedof the elevator will be very low, -due to the rapid flow of liquidthrough the `bypass means, while if the elevator is empty, or verylightly loaded, the .small back pressure will produce a relatively Slowow through the bypass means 24 Vand a Acorrespondingly rapid travel ofthe elevator in the ,leveling zone. This speed variation is eliminatedby the ow regulator valves 27, 28 and 29, all of which are structurallyalike, so that only the valve 27 will be described in detail withreference to Figure '2.

The flow regulator valve `27 consists of a mai-n valve body 32 whichincludes a hollow, internally Ithreaded inlet portion V33, -a hollowcasing portion 34 of smaller external diameter than the inlet portion,and a hollow, internally threaded outlet lpor-tion 35 of intermediateoutside diameter. The casing portion 34 has a cavity 34a which is indirect communicationY with the -hollow inlet portion 33, but which isvseparated from direct communication -with'the hollow outlet portion 35of the body by a transverse -wall 34h. At l,one end of the casingportion 34 is .a group .of radiallyV extending liquidV outow passages 36which communicate -vvith an annular vvmanifold `37 :the `inner wall oftwhich is-dened by the casing 34^Sand the .outer wall of which isdefined by an outer sleeve 38 which seats on an external shoulder 33a ofthe inlet portion .33 of the `valve body 32. A snap rring 39 engages theother .end of the sleeve and is seated ina recess in .the .outlet endportion 35 of the valve body. From the annular manifold 37 -liquid maypass through a :second group Eof liquid .passages 4.0 Awhich opens.directly into .an .outlet ,bore :35a of the outlet end portion 35 ofthe valve body 32. Thus, liquid may flow into the lhollow ,inlet portion33, through .the liquid passages 36, the annular manifold .37, theliquid passages 40 and out through :the outlet bore 35a.

Control of .the flow .of liquid `through .the ow regulator `valve iseffected by 'means of a cup-like valve piston 41 which has an end wall4Z provided with an axial opening 43 and a group of radially extendingliquid `ports 44. A snap -ring 45 in the hollow inlet pipe portion 33acts as a seat for .the valve piston 41, against which the piston isresiliently urged by a valve spring 46 in the chamber 34a. When thevalve piston 41 is seated on the Y ange 45 the liquid ports i4 areprecisely aligned with the liquid outlet passages 36 `in Vthe casing,34, so that in this position of the Vvalve piston a maximum Vflow ofliquid through the iiow regulator valve is permitted. The spring 46 `isso calibrated `as yto retain the valve piston 4l on the ring 45 whenthere is a minimum load the elevator car 13. Increase in the load ontheelevator car 13 .produces an increasing backl pressure against the endwall 4'2 of the valve piston 41, land moves the vvalve piston in such amanner as to lreduce the effective area of the liquid flow passages 36.Thus., the available outflow passage area varies linversely with respectto :the

back pressure on the lpiston end .-wall 42 caused by the load in theelevator car 13. Y

The system shown in the patent drawings uses three ow `regulator valvesso that each vmay be of relatively small capacity, and between them theyare adequate to carry the total volume of liquid adapted to be bypassedthrough the solenoid bypass valve Z6.

The system is valso provided with an over pressure relief 'valve 47,l'in the conventional manner, which is set to open at a pressure about10% above 'the normal operating pressure for the system, vso that ifthere is any failure of the normal operating valves-the relief valvewill prevent damage to the system.

The foregoing detailed description is given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom, as some modifications will be obvious to those skilled in theart.

I claim:

1. In an operating system for controlling the delivery of liquid to thecylinder and plunger of a hydraulic elevator to control its ascent fromstation to station and its leveling at a station in the course of suchascent: a constant delivery pump to delivery liquid under pressure; abypass line; a normally closed bypass valve between said pump and saidbypass line; means for opening said bypass valve to admit liquid to said'bypass line when the rising plunger reaches a predetermined point atwhich a reduced rate of rise is desired; and a flow regulator valve insaid line downstream from the bypassrvalve, said flow regulator valvehaving a liquid passage and means for modifying the available area ofsaid passage 6 inversely with respect to back pressure at the pumpoutlet, whereby the rate at which liquid is bypassed remainssubstantially constant with variations in said back pressure.

` 2. The mechanism yof claim 1 in which the ow regulator valve includesa longitudinally movable valve piston and spring means urging saidpiston to a position at which the liquid passage in the valve is fullyopen, said spring means being calibrated to permit movement of thepiston to reduce the available area of the liquid passage Iwhen backpressure on the piston exceeds a predetermined minimum value.

References Cited in the file of this patent UNITED STATES PATENTS MoranNov. 6, 1951

